Air-conditioning loop with gas accumulator

ABSTRACT

An air-conditioning loop with a transcritical refrigerant including a compressor, a gas cooler, an evaporator, an expansion device, an internal heat exchanger for heat exchange between a high-pressure side and a low-pressure side, an accumulator on the low-pressure side between evaporator and the internal heat exchanger, and a gas accumulator on the low-pressure side.

CROSS REFERENCE TO RELATED APPLICATION(S)

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO A MICROFICHE APPENDIX

Not applicable.

TECHNICAL FIELD

The present invention relates to an air-conditioning loop, and particularly to a vehicle air-conditioning loop with a transcritical refrigerant.

BACKGROUND OF THE INVENTION AND TECHNICAL PROBLEMS POSED BY THE PRIOR ART

Air-conditioning loops are, of course, well known. Further, such air-conditioning loops with a transcritical refrigerant are also known, especially for use in a vehicle. Broadly, such loops include a compressor, a gas cooler, an evaporator, an expansion device, an accumulator and an internal heat exchanger, which serve to exchange heat between a high pressure side a low pressure side.

One such arrangement was described in a filing with the German Patent and Trademark Office (given file number DE 2005 021 787.7), which principally describes a particular internal heat exchanger having an accumulator function. The accumulator separates liquid refrigerant coming from the evaporator and stores it to ensure that exclusively gaseous refrigerant is fed to the compressor in order to guarantee its function.

German Patent Application (file number DE 10 2005 021 464.9) also describes an internal heat exchanger.

When an internal heat exchanger (IHE) is used, the accumulator ensures that the refrigerant fed to the low-pressure part of the internal heat exchanger is either gaseous or a two-phase mixture with high vapor fraction in order to ensure high efficiency of the air conditioner. The remaining liquid refrigerant is deposited in the accumulator and forms a buffer in order to cover the different refrigerant demands of the loop under different operating conditions and especially to compensate for the loss of refrigerant from leaks over a longer operating time of the air conditioner.

For air conditioners that operate without thermally-regulated expansion devices, such liquid separation on the low-pressure side may be sufficient. However, especially for transcritical coolant loops, a much larger accumulator vessel must be provided to accommodate the refrigerant (CO₂) at high ambient temperatures than is necessary for liquid storage. The accumulator vessel therefore functions as a supercritical gas accumulator in the switched-off state and a liquid accumulator or separator when the unit is in operation.

Because of the different environmental regulations world-wide, automobile manufacturers need to be able to equip automobiles with ordinary air conditioners that use chlorofluorohydrocarbons as refrigerant in some markets, and CO₂ air conditioners in other markets. Of course, efficient manufacturing requires consistence of space requirements within a model series of automobiles, and changing space requirements for different markets is highly undesirable not only for cost reasons but also market recognition. Certainly, it is undesirable to have to significantly change the automobile design for a model series in order to accommodate different air-conditioners required in different markets.

Air conditioners with a thermal expansion device now common on the market use so-called receivers (i.e., liquid accumulators that are integrated by design into the condenser with a supercooling zone) which are generally elongated cylindrical vessels.

The present invention is directed toward overcoming one or more of the problems set forth above.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, an air-conditioning loop with a transcritical refrigerant is provided, including a compressor, a gas cooler, an evaporator, an expansion device, an internal heat exchanger for heat exchange between a high-pressure side and a low-pressure side, and an accumulator on the low-pressure side between evaporator and the internal heat exchanger, wherein a gas accumulator is provided on the low-pressure side.

In one form of this aspect of the present invention, the gas accumulator is connected by a branch line to the line between the internal heat exchanger and compressor.

In another form of this aspect of the present invention, the gas accumulator is a line thickening between the internal heat exchanger and the compressor.

In still another form of this aspect of the present invention, the gas accumulator is integrated with the gas cooler.

In yet another form of this aspect of the present invention, the gas accumulator is situated between the internal heat exchanger and the intake side of the compressor. In a further form, the gas accumulator is connected by a branch line to the line between the internal heat exchanger and compressor.

In another form of this aspect of the present invention, the gas accumulator is integrated in the internal heat exchanger. In a further form, the internal heat exchanger includes a first tube with a multi-chamber tube extending therethrough with the high-pressure side flowing through the multi-chamber tube, and the first tube includes a low-pressure flow path occupying part of the tube cross-section adjacent the multi-chamber tube with the remaining cross-section of the first tube being a gas accumulator connected to the low-pressure side.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a first cooling loop having a gas accumulator incorporated therein in one position on the low pressure side;

FIG. 2 schematically illustrates a second cooling loop having a gas accumulator incorporated therein in a second position on the low pressure side;

FIG. 3 schematically illustrates a third cooling loop having a gas accumulator incorporated therein in a third position on the low pressure side;

FIG. 4 schematically illustrates a fourth cooling loop having a gas accumulator incorporated therein in a fourth position on the low pressure side; and

FIG. 5 shows a cross-section through a gas accumulator which is active as an internal heat exchanger.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 to 4 illustrate various arrangements of the air-conditioning loops such as may be especially used in a vehicle, with a transcritical refrigerant. The loops each include a compressor 10, a gas cooler 12, an evaporator 14, an expansion device and internal heat exchanger 20 (for heat exchange between a high-pressure side HD and a low-pressure side ND), and an accumulator 26 (on the low-pressure side between the evaporator 14 and the internal heat exchanger 20). Air-conditioning loops such as illustrated in these Figures generally correspond to prior art air conditioning loops.

However, in accordance with one feature of the present invention, the holding capacity of the accumulator 26 is different than those used in the prior art. For example, in one practical example used in the prior art (in which the air conditioner is located in a passenger car), the holding capacity and the space requirements for the accumulator connected with it is about 500-800 mL. By contrast, the holding capacity of the accumulator 26 variously depicted in FIGS. 1 to 4 is reduced to about 200-400 mL, leading to a significant space savings, particularly in vehicles, where space available for the various automotive systems is extremely limited (and interdependent, since increasing the size of one component will frequently require that the size of another component be decreased, or that some other component be moved in an already crowded space).

In accordance with the loop illustrated in FIG. 1, the gas accumulator 30 is mounted by means of a branch line 40 on the line between the internal heat exchanger 20 and the intake side of the compressor 10. In this practical example, the holding capacity of the accumulator 26 is about 200-350 mL, which is sufficient in order to be able to compensate for the loss of refrigerant over the required period. The space savings obtained is primarily attributed to the fact that the two relatively small vessels can be arranged individually in available niches.

In the practical example illustrated in FIG. 2, a branch line 40 is also provided in order to incorporate the gas accumulator 30 on the low-pressure side ND. In contrast to FIG. 1, the gas accumulator 30 in FIG. 2 is combined with the gas cooler 12. Further, the gas accumulator 30 may be a narrow tube parallel to one of the collecting tanks of the gas cooler 12 (not shown).

In the practical example illustrated in FIG. 3, the gas accumulator 30 is traversed by the entire gaseous refrigerant. It can, for example, be designed as a partial line thickening.

In the practical example illustrated in FIG. 4 the gas accumulator 30 is combined with the internal heat exchanger 20.

FIG. 5 illustrates a cross-section through an internal heat-exchanger 20 having the gas accumulator 30 according to a particularly advantageous embodiment of the present invention. This embodiment includes a long, narrow, round (and therefore pressure-stable) tube 42. The high-pressure side HD flows through a flat multi-chamber tube 44 arranged centrally in the tube 42. The low pressure side ND flows through a flow path 46 divided on both sides of the flat multi-chamber tube 44, which is filled with an internal insert 48. Two thin longitudinal partitions 56 with beveled longitudinal edges 58 are suitably joined by soldering to the inside wall of the tube 42, and separate the low-pressure flow path 46.

As is apparent from FIG. 5, the remaining cross-section of the tube 42, roughly half the entire tube cross-section, remains available for use as the gas accumulator 30, with corresponding openings (not shown) being present in the longitudinal partitions 56 in order to produce a connection between the low-pressure flow path and the low-pressure gas accumulator 30.

The gas accumulator 30 integrated in the internal heat exchanger 20 also has a connection (not shown) to the intake side of compressor 10. This device, designed as an advantageous solder design, is characterized by particular ease of manufacture and is highly effective as an internal heat exchanger 20.

Additional details with reference to the solder construction can be taken from German Patent Application (File Number DE 10 2005 021 464.9), the disclosure of which is hereby fully incorporated by reference, which application relates to a device for intermediate cooling of the refrigerant (which device may be used conjunction with this application, as stated above, as a gas accumulator/internal heat exchanger).

It should be appreciated that the present invention in at least one aspect may provide an air-conditioning loop with a transcritical refrigerant which may be accommodated in the same design space as an air conditioner with ordinary refrigerant. Moreover, a gas accumulator may be provided which has an external shape favorable for positioning in the design space and can also be integrated at any location in the vehicle, for example on the gas cooler.

Still other aspects, objects, and advantages of the present invention can be obtained from a study of the specification, the drawings, and the appended claims. It should be understood, however, that the present invention could be used in alternate forms where less than all of the objects and advantages of the present invention and preferred embodiment as described above would be obtained. 

1. An air-conditioning loop with a transcritical refrigerant comprising a compressor, a gas cooler, an evaporator, an expansion device and internal heat exchanger for heat exchange between a high-pressure side and a low-pressure side, and an accumulator on the low-pressure side between evaporator and the internal heat exchanger, wherein the improvement comprises a gas accumulator on the low-pressure side.
 2. The air-conditioning loop of claim 1, wherein the gas accumulator is connected by a branch line to the line between the internal heat exchanger and compressor.
 3. The air-conditioning loop of claim 1, wherein the gas accumulator is a line thickening between the internal heat exchanger and the compressor.
 4. The air-conditioning loop of claim 1, wherein the gas accumulator is integrated with the gas cooler.
 5. The air-conditioning loop of claim 1, wherein the gas accumulator is situated between the internal heat exchanger and the intake side of the compressor.
 6. The air-conditioning loop of claim 5, wherein the gas accumulator is connected by a branch line to the line between the internal heat exchanger and compressor.
 7. The air-conditioning loop of claim 1, wherein the gas accumulator is integrated in the internal heat exchanger.
 8. The air-conditioning loop of claim 7, wherein the internal heat exchanger includes a first tube with a multi-chamber tube extending therethrough with said high-pressure side flowing through said multi-chamber tube, and the first tube includes a low-pressure flow path occupying part of the tube cross-section adjacent the multi-chamber tube with the remaining cross-section of the first tube being a gas accumulator connected to the low-pressure side. 